Finding candidates to replace their microcode

By: Dresdenboy (M.Waldhauer.delete@this.gmx.de), August 19, 2004 10:59 am
Room: Moderated Discussions
Paul DeMone (pdemone@igs.net) on 8/19/04 wrote:
---------------------------
>Dresdenboy (M.Waldhauer@gmx.de) on 8/19/04 wrote:
>---------------------------
>>According to my idea to use microcode patching to create customized instructions,
>>which use microcode to do things more efficient than it would be possible with x86
>>code (e.g. MUL), I think that there are several nice candidates. We just have to
>>look for vector decoded x87 or MMX codes.
>
>Ahhh, the home fallout shelter of computer science.

OK, you got me. I admit to have used a too general meaning of "my idea". My idea was just to use microcode patching on some of todays x86 CPUs for a specific task and doing not much.

>Customizing and/or extending vendor instructions sets
>in application specific fashion using microcode is a
>very old idea in computers and this capability has been
>offered by vendors several times in the past. Writing

I remember Alpha, VIA and NexGen MPUs to have such features besides many others. I don't remember correctly the intentions for the Alpha, but VIA included this feature clearly to be used by programmers to optimize code.

>So IMO it didn't make sense 30 years ago and it makes
>even less sense today.

Sure, it doesn't make sense as an general option, because the microcode might get outdated with the CPU generation. However, for an algorithm, which is running 24/7 on a lot of systems and which could be accelerated by 5-10% thanks to some custom microcode, this would surely make sense.

But I won't put energy into this idea before more details appear. Currently the other guys working on this algorithm and I myself just try to optimize it as good as possible.

BTW, the code contains ~30% register copying MOV instructions. I'd like to see x86 MPUs address this wasting of execution units in the future.
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TopicPosted ByDate
Opteron Exposed: Reverse Engineering AMD K8 Microcode UpdatesAnonymous2004/07/22 01:39 AM
  Opteron Exposed: Reverse Engineering AMD K8 MicrocDresdenboy2004/07/22 05:13 AM
    Opteron Exposed: Reverse Engineering AMD K8 MicrocAK2004/07/22 08:49 AM
      Opteron Exposed: Reverse Engineering AMD K8 MicrocDresdenboy2004/07/22 10:26 AM
        the former posting has no new text, continue hereDresdenboy2004/07/22 10:32 AM
  An additionDresdenboy2004/07/22 08:04 AM
    An additionAnonymous2004/07/22 02:32 PM
      An additionDresdenboy2004/07/22 02:55 PM
  Opteron Exposed: Reverse Engineering AMD K8 Microctom vier2004/07/22 08:38 AM
    Opteron Exposed: Reverse Engineering AMD K8 MicrocWouter Tinus2004/07/22 08:56 AM
    Opteron Exposed: Reverse Engineering AMD K8 MicrocIgor2004/07/23 10:00 PM
      Opteron Exposed: Reverse Engineering AMD K8 MicrocKronos2004/07/24 02:04 PM
  Opteron Exposed: Reverse Engineering AMD K8 Microcode UpdatesMax2004/07/22 01:01 PM
    Opteron Exposed: Reverse Engineering AMD K8 Microcode UpdatesAnonymous2004/07/22 05:26 PM
  Does that means..._Arthur2004/07/22 10:01 PM
    Does that means...Dresdenboy2004/07/23 03:27 AM
    Does that means...Jan2004/07/23 07:51 AM
      Does that means...Anonymous2004/07/23 03:10 PM
        Does that means...Igor2004/07/23 10:42 PM
          Does that means...Anonymous2004/07/24 09:53 PM
            Does that means...Igor2004/07/25 12:08 AM
            Does that means...Anonymous2004/07/25 12:17 AM
              Does that means...anonymous2004/07/25 04:31 PM
                Does that means...Igor2004/07/26 08:42 PM
  Permanent virusess.chauhan2004/07/27 12:25 AM
    Permanent virusesAnonymous2004/07/27 10:42 AM
  Finding candidates to replace their microcodeDresdenboy2004/08/19 02:06 AM
    Finding candidates to replace their microcodePaul DeMone2004/08/19 06:22 AM
      Finding candidates to replace their microcodeDavid Kanter2004/08/19 06:53 AM
        Finding candidates to replace their microcodefoobar2004/08/19 09:55 AM
          Finding candidates to replace their microcodeDavid Kanter2004/08/19 10:58 AM
          Finding candidates to replace their microcodeAnonymous2004/08/20 01:56 PM
            Finding candidates to replace their microcodehobold2004/08/23 03:14 PM
      Finding candidates to replace their microcodeDresdenboy2004/08/19 10:59 AM
        Finding candidates to replace their microcodeanonymous2004/08/19 03:35 PM
        Finding candidates to replace their microcodeAnonymous2004/08/20 02:23 PM
          Finding candidates to replace their microcodeGroo2004/08/20 09:25 PM
          Finding candidates to replace their microcodeDresdenboy2004/08/21 05:01 AM
            Finding candidates to replace their microcodeAnonymous2004/08/21 04:45 PM
              Finding candidates to replace their microcodeanonymous2004/08/21 09:45 PM
      Finding candidates to replace their microcodeMatt Craighead2004/08/19 01:18 PM
      Finding candidates to replace their microcodeRick C. Hodgin2004/08/21 04:58 AM
        Finding candidates to replace their microcodeanonymous2004/08/21 09:41 PM
          Finding candidates to replace their microcodeRick C. Hodgin2004/08/22 08:31 AM
            Finding candidates to replace their microcodeanonymous2004/08/23 08:56 AM
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